尖椒叶片叶绿素含量的近红外检测分析实验研究

Measurement of Chlorophyll Content in Pepper Leaves by Near Infrared Analysis

应用傅里叶漫反射近红外光谱技术探讨了尖椒叶片叶绿素含量的无损检测方法。利用偏最小二乘法和主成分回归法分别建立了尖椒叶片叶绿素含量与漫反射光谱间的数学模型,同时对不同光谱预处理方法和不同建模波段范围对模型的预测性能进行对比分析。结果表明,用傅里叶变换光谱仪采集的原始光谱经平滑和基线校正对结果的影响不是很明显;利用PLS建模获得的结果明显好于采用PCR方法建模;原始光谱经二阶微分获得的预测结果比一阶微分光谱和原始光谱的预测结果好;剔除异常样本后,在全波段范围内原始光谱经二次微分的预测相关系数达到0.975 37,校正均方根误差和预测均方根误差分别为2.33和5.49。本研究说明,应用近红外漫反射光谱检测叶片叶绿素含量是可行的,可为今后快速无损检测叶片叶绿素含量提供理论依据。

The objective of this research was to study the potential of NIR diffuse reflectance spectroscopy for nondestructive measurement of chlorophyll content in pepper leaves. Statistical models were developed using partial least squares （PLS） and principal component regression （PCR） analysis technique, and four different mathematical treatments were used in spectra processing： smoothing, baseline correction, different wavelength range, and first and second derivative. The results showed that smoothing and baseline correction of NIR original spectra had little influence on spectral data analyzing, second derivative spectra showed better results than first derivative spectra and original spectra, while PLS analysis could get better modeling results than PCR analysis. The best calibration model was obtained after removing four outlier samples, and processing spectra with second derivate in the full wavelength range, with the highest correlation coefficient （r=0.975 37）, a relative lower RMSEC value （2. 33）, and a small difference between RMSEC （2. 33） and RMSEP （5.49）. It can be concluded that NIR technique is a feasible, nondestructive way to predict the chlorophyll content in pepper leaves.